The present invention relates to a direct injection type of fuel injector and, an internal combustion engine mounting a direct injection type of fuel injector; and, more particularly, the invention relates to a fuel injector for forming a fuel spray having a superior ignition property and a superior combustion property, and an internal combustion engine on which the fuel injector is mounted. The invention also relates to a fuel swirl type injector structure for injecting fuel directly into a combustion chamber-of a direct injection, fuel injector type, internal combustion engine, and an internal combustion engine on which the fuel injector is mounted.
In contrast to a fuel injection apparatus of the type which is used to inject fuel into an air intake conduit of an internal combustion engine, there is also a direct injection type of fuel injection apparatus by which fuel is injected directly into a combustion chamber of the engine.
An example of a direct injection gasoline internal combustion engine is disclosed in Japanese application patent laid-open publication No. Hei 6-146886. In this document, a construction is described in which, by taking into consideration the installation position of the fuel injector relative to an air intake port in an upper portion of the cylinder, a longitudinal swirl air intake flow (a tumble flow) from an air intake opening is produced in a combustion chamber, and by using a fuel thinner than a theoretical mixture of fuel and air, a lean-burn combustion can be carried out stably and fuel consumption can be improved.
Further, Japanese application patent laid-open publication No. Hei 8-42427 discloses a fuel injector in which an orifice edge of a nozzle member is formed with a two-dimensional curved face which is perpendicular to a valve body axial line so that a flat spray having an elliptical cross-sectional shape is generated, whereby fuel adhesion to the air intake valve is restrained.
In the above-stated publications, full consideration has not been given to the spray shape or the injection structure, to the extent that both the ignition property (a spark property) and the combustion property (an unburned gas discharge amount reduction) can be improved. Namely, a full examination has not been made concerning the means for generating a spray having a cross-sectional shape which is adapted to the cylinder piston shape and cavity shape in the engine, under a state where rough particles in the spray are reduced.
To optimize the spray which is injected by a fuel injector, it is necessary to take into consideration the following characteristics or properties of the spray. A first characteristic relates to the spray shape and spray spreading angle, and the distance the spray reaches. A second characteristic relates to the spray particle diameter. In this regard, it is necessary to improve the uniformity of the spray particle diameter distribution to reduce the number of large diameter particles in the spray as soon as possible. A third characteristic relates to the spray structure. In this regard, it is necessary to produce a proper spatial distribution of the sprayed fuel particles in the combustion chamber.
The inventors of the present invention have studied how the above-stated spray properties relate to the combustion property of the internal combustion engine according to experimental analysis, and the following facts have been made clear. To effect an improvement in the ignition property, it is effective to locate the major part of the fuel particle distribution in the vicinity of the spark plug and to make the air-fuel distribution high in the spark plug direction.
In addition, when the fuel particle distribution in the piston direction is lessened, there is a tendency for unburned gas components (HC, CO) in the fuel to be reduced, so that the combustion property is improved.
An object of the present invention is to provide a direct injection type of fuel injector and an internal combustion engine on which the fuel injector is mounted, wherein a fuel spray which results in a reduced discharge amount of unburned gas components can be formed.
To attain the above-stated object, according to the present invention, at an orifice edge of a nozzle member of a fuel injector, a constriction of the spray flow is opened partially. At the injector nozzle, a center axial line of the orifice and a flat face in parallel to the center axial line of the fuel injector serves as a boundary, and, at one side of the boundary, the spray amount is large, and at the other side of the boundary, the spray amount is small, whereby the spray angle is large in a direction parallel to the flat face and the spray angle is small in a direction transverse to the flat face, namely a flat inclined spray is formed.
More specifically, to a nozzle end face in which an outlet opening face of the orifice is formed, a V-groove is formed by two faces which incline at an optional angle relative to the center axial line of the orifice, or a substantially recess-shaped step-wise rectangular groove having different cut-off depths is formed.
As a result, in the groove direction, the constriction of the spray flow can be opened, so that at a side of a large inclination angle or a side of a rectangular groove having a deep cut-off depth, the spray amount is large, but at a side of a small inclination angle or a side of a rectangular groove having a shallow cut-off depth, the spray amount is small, namely a flat inclined spray is formed.
To allow the spray to directly reach the ignition device, or to reach the ignition device as a result of the induction produced by a cavity which is formed on the piston, the spray angle can be adjusted; and, accordingly, it is possible to obtain a good ignition property in the internal combustion engine and to reduce the discharge amount of unburned gas components of combustion.